You have to understand, he didn't know what it was going to do to him or Doomsday. What he did know however was that if the nuke could kill Doomsday it could certainly kill him too. That's where the sacrifice part is.

I'm not saying the trailer isn't going to be released in the next days/hours, but are you sure they didn't just add "In theaters March 25th" or something like that ? Because in addition to BvS, How to be single, Midnight Special, The Nice Guys, and Fantastic Beasts were also "updated today".

J. Michael Straczynski with Superman: Grounded. The first half is a meaningful story about Superman walking across the USA and reconnecting with its citizens. The second half (written by Chris Roberson) just shit allover the first, destroy the work of Straczynski (knowing what is coming, I simply can't enjoy the first half anymore), and add an unnecessary vilain.

The Kryptonians gained their powers once they were exposed to the sun, but what you have to remember is that they have helmets. Their helmets seem to filter electromagnetic and sound waves (but let the sun's radiation pass it seems), and when they take them off (Zod broke his during his first fight against superman, same for Faora) their is no more filter for all those waves, so they see them and hear them all at the same time and what happened to Clark during his childhood happens to them now.

And Clark is clearly more powerfull than Zod, the end of the film tells you that. He couldn't have snapped Zod's neck with such force without being stronger than Zod. But Clark never really used his powers in this world, he never mastered them and never learned how to fight. During Faroa's fight he is very clumsy, he is not aware of his surroundings and seems overwhelmed by everything happening around him. Raw strength can't balance that, and even if it could, Clark's major personnality trait is to hold back. Clark hold back all the time. The only time when it is not the case is at the end, when Zod put him in a corner and give him no other choice but to kill him.

If Zod's mental health problems are not a suitable answer for you, maybe you will like this one.

During Zod's explanations of what they did prior to comming to Earth you can see where they found the world engine. You can see that this planet was totally lifeless, there was no atmosphere. So why didn't they use the world engine ? Well, I think they simply couldn't use it. I think the world engine can modify an atmosphere but not create one (or it can't create a magnetic field who can sustain this atmosphere).

There is also the possibility that they did not have a lot of energy left and Earth can easily be transformed into a second Krypton.